A printing device capable of printing on tape, tubing, and the like is well known in the art. A tape-printing device described in Japanese Patent Application Publication. No. 2014-233930 employs a DC motor to drive a tape-conveying roller. When power is supplied to the DC motor, the motor rotates the tape-conveying roller, and the roller conveys a surface layer tape and an ink ribbon simultaneously. The tape-printing device also includes a thermal head having a plurality of heating elements. Electricity is conducted to the heating elements as the surface layer tape and ink ribbon are conveyed, causing ink to be transferred in units of dots from the ink ribbon to the surface layer tape. The timing for transferring the dots is synchronized with a pulse signal outputted from an encoder mounted on the DC motor. Hereinafter, this style of printing method will be called “synchronous printing.” Thus, the tape-printing device prints surface layer tape according to synchronous printing.
During the course of the printing process, printing and conveyance may be temporarily halted and subsequently resumed. When the supply of power to the DC motor is halted, causing the DC motor to decelerate, the rotational speed of the DC motor may diverge from the conveying speed of the tape conveyed by the roller as the tape-conveying roller continues to rotate due to inertia. When synchronous printing is performed continuously during such cases, undesirable white lines (areas in which dots are not formed) may be produced. In light of this, the conventional tape-printing device described above determines whether the rotational speed of the DC motor has diverged from the tape conveying speed based on the pulse period of the pulse signal outputted from the encoder. The tape-printing device continues to execute synchronous printing while the period of the pulse signal does not meet a prescribed condition. However, when the period of the pulse signal meets the prescribed condition, the tape-printing device switches from synchronous printing to timer printing for transferring dots at a prescribed period.